Barrel length and twist rate are both contributing factors for velocity. The tighter that twist is, and the longer that barrel is, the longer and faster that bullet starts spinning.... For example, a .308 with 175gr bullets with an 11.25" twist 24" barrel will produce higher velocity and greater accuracy at distance, b/c it won't start tumbling as soon as say a 11.25" 20" barrel...

Yes, all different calibers have different FPS variations depending on twist, barrel length, load data, etc... All the different calibers that use the same diameter bullet all have differences. You have to get VERY specific when it comes to your gun. Every gun is individual. Every gun will shoot different, even if it is 2 identical guns made consecutively by the same gunsmith. It's the nature of the beast.

__________________
"I'm just a peckerwood who lives in the hills with too many guns..." - Bob Lee Swagger

Barrel length and twist rate are both contributing factors for velocity. The tighter that twist is, and the longer that barrel is, the longer and faster that bullet starts spinning.... For example, a .308 with 175gr bullets with an 11.25" twist 24" barrel will produce higher velocity and greater accuracy at distance, b/c it won't start tumbling as soon as say a 11.25" 20" barrel...

Yes, all different calibers have different FPS variations depending on twist, barrel length, load data, etc... All the different calibers that use the same diameter bullet all have differences. You have to get VERY specific when it comes to your gun. Every gun is individual. Every gun will shoot different, even if it is 2 identical guns made consecutively by the same gunsmith. It's the nature of the beast.

Actually barrel length has nothing to with how fast a bullet spins other than longer barrels usually produce more velocity which spin the bullet faster.

My question is for example, how much slower will a barrel with a 9 twist push a bullet then the same type of barrel with a 10 twist pushing the same bullet? 10 fps? 30 fps? 50 fps?

__________________
- Mark

You will never know how much it has cost my generation to preserve your freedom. I hope you make good use of it.
~ John Quincy Adams

Given the difference that you can experience from one barrel to next in the same production. How would a guy ever quantify that? When you change barrels your entering a whole new set of controls, so your results are going to be different to a point.

__________________
Keep in mind the animals we shoot for food and display are not bullet proof. Contrary to popular belief, they bleed and die just like they did a hundred years ago. Being competent with a given rifle is far more important than impressive ballistics and poor shootability. High velocity misses never put a steak in the freezer.

I agree that it would be hard to quantify a different velocity, the faster spin will stabilize longer and heavier bullets. They go slower because they are heavier. The only reason for the faster twist is to stabilize. I have a 22-243 with a 7 twist that shoots 80g bergers quite well but if I shoot 52 g bullets, some spin apart before getting to the target.

__________________
Phil Conklin.... Shooting Instructor for The Best of the West

Actually barrel length has nothing to with how fast a bullet spins other than longer barrels usually produce more velocity which spin the bullet faster.

My question is for example, how much slower will a barrel with a 9 twist push a bullet then the same type of barrel with a 10 twist pushing the same bullet? 10 fps? 30 fps? 50 fps?

You misunderstood....The bullet SPINS faster from a longer barrel BECAUSE there is more time it is touching the rifling and being acted upon by the rifling force for stabilization purposes. The rifling actually slows the bullet down slightly other than if it were a smooth-bore gun, b/c the rifling is actually biting into the bullet's jacket. So rifling has a very very miniscule affect on the velocity.

__________________
"I'm just a peckerwood who lives in the hills with too many guns..." - Bob Lee Swagger